1. Field of the Invention
The present invention relates to a surface discharge plasma display panel (hereinafter referred to as a surface discharge PDP) having a matrix display form, and a method for manufacturing such a plasma display panel.
The surface discharge PDPs are PDPs wherein paired display electrodes defining a primary discharge cell are located adjacent to each other on a single substrate. Since such PDPs can serve adequately as color displays by using phosphors, they are widely used as thin picture display devices for television. And since, in addition, PDPs are the displays that are the most likely to be used as large screen display devices for high-vision pictures, there is, under these circumstances, a demand for PDPs for which the quality of their displays has been improved by increasing resolution and screen size, and by enhancing contrast.
2. Related Arts
FIG. 14 is a cross sectional view of the internal structure of a conventional PDP 90. A PDP 90 is a surface discharge PDP having a three-electrode structure and a matrix display form, and is categorized as a reflection PDP according to the form of its phosphors arrangements.
On the front of a PDP 90, on an internal surface of a glass substrate 11, paired display electrodes X and Y are positioned parallel to each other and arranged for each line of a matrix display so that they cause a surface discharge along the surface of the glass substrate 11. A dielectric layer 17, for AC driving, is formed to cover the paired display electrodes X and Y and separate them from a discharge space 30. A protective film 18 is formed on the surface of the dielectric layer 17 by evaporation. The dielectric layer 17 and the protective film 18 are transparent.
Each of the display electrodes X and Y comprises a wide, linear transparent electrode 41, formed of an ITO thin film, and a narrow, linear bus electrode 42, formed of a thin metal film (Cr/Cu/Cr). The bus electrode 42 is an auxiliary electrode used to acquire an appropriate conductivity, and is located at the edge of the transparent electrode 41, away from the plane discharge gap. With such an electrode structure, the blocking of display light can be reduced to the minimum, while the surface discharge area can be expanded to increase the light emission efficiency.
At the rear, an address electrode A is provided on the internal surface of a glass substrate 21 so that it intersects at a right angle the paired display electrodes X and Y. A phosphors layer 28 is formed on and covers the glass substrate 21, including the upper portion of the address electrode A. A counter discharge between the address electrode A and the display electrode Y controls a condition wherein wall charges are accumulated in the dielectric layer 17. When the phosphors layer 28 is partially excited by an ultraviolet ray UV that occurs as a result of a surface discharge, it produces visible light emissions having predetermined colors. The visible light emissions that are transmitted through the glass substrate 11 constitute the display light.
A gap S1 between paired display electrodes X and Y arranged in a line is called a "discharge slit," and the width w1 of the discharge slit S1 (the width in the direction in which the paired display electrodes X and Y are arranged opposite each other) is so selected that a surface discharge occurs with a drive voltage of 100 to 200 V applied to the display electrodes. A gap S2 between a line of paired electrodes X and Y and an adjacent line is called a "reverse slit," and has a width w2 greater than the width w1 of the discharge slit S1, that is sufficient to prevent a discharge between the display electrodes X and Y that are arranged on opposite sides of the reverse slit S2. Since paired display electrodes X and Y are arranged in a line with a discharge slit S1 between them, and a line is separated from another line by reverse slits S2, each of the lines can be rendered luminous selectively. Therefore, portions of the display screen that correspond to the reverse slits S2 are non-luminous areas or non-display areas, and the portions that correspond to the display slits S1 are luminous areas or display areas.
From the front of a conventional panel structure, a phosphors layer 28 in the non-luminescent state is visible through the reverse slits S2. And the phosphors layer 28 in the non-luminescent state has a white or light gray color. Therefore, when a conventional display panel is used in an especially bright place, external light is scattered at the phosphors layer 28 and the non-luminescent areas between lines has a whitish color, which results in the deterioration of the contrast of the display.
As a method for increasing the contrast for a color display PDP, proposed are a method for providing a color filter by coating the outer surface of the substrate 11 on the front with a translucent paint that corresponds to the luminous color of a phosphors; a method for arranging on the front face of a PDP a filter that is fabricated separately; and a method for coloring a dielectric layer 17 with colors R, G and B.
It is, however, very difficult to apply coats of individually colored paints at locations corresponding to minute pixels. In case of the separate filter on the front, a gap between the PDP and the filter causes distortion in display images. And in case of the coloring of the dielectric layer 17, since the tints of coloring agents (pigments) differ, uniformity of permittivity is deteriorated by coloring, and a discharge characteristic is rendered unstable. In addition, positioning is also difficult when coloring a dielectric layer, just as the coating of colored paints.